Combined air cooled condenser

ABSTRACT

The invention relates to an air cooled condenser system that contains a steam-air heat exchanger ( 3 ) consisting of tubes ( 2 ) finned on the outside for the partial direct condensing of steam ( 1 ) with ambient air ( 4 ). This heat exchanger ( 3 ) receives the steam ( 1 ) from an upper distribution chamber ( 24 ) and ends in a lower chamber ( 25 ) which collects the condensate ( 8 ) and the steam ( 27 ) that has not yet condensed. The steam ( 22 ) not yet condensed in the steam-air heat exchanger ( 3 ) is condensed, in the steam-air section of the air cooled condenser, in a space operating as a direct contact condenser ( 9 ) by spraying water from the water-air cooling section ( 7 ) of the air cooled condenser, where the non-condensing gases are removed as well. The water ( 13 ) heated up in the direct contact condenser ( 9 ) is re-cooled in a water-air heat exchanger ( 7 ).

1. TECHNICAL FIELD

The subject of the invention relates to an air cooling system of powerplant or industrial cycles. It carries out the condensation of thesteam-state medium (generally water vapour) in the way described in theclaims.

2. BACKGROUND ART

For the realisation of numerous industrial, but primarily thermal powerstation processes it is necessary to extract heat from the process atthe ambient temperature level usually via the condensation of thesteam-state operating medium of these processes. The traditionalsolutions involve exceptionally intensive use of water (evaporative oronce-through cooling), which, due to environmental protectionconsiderations or the lack of the required amount of water, may causeproblems in numerous cases. In order to overcome this various well knownand tried dry cooling systems were developed.

The most wide-spread dry cooling system is the so-called direct drycooling. In this cooling method, if it serves power plant cycles, thewater vapour, expanded in a steam turbine subjected to a vacuum, exitsfrom the turbine through a steam pipe with a large diameter, thenthrough an upper distribution chamber it goes into a so-called steam-airheat exchanger. The steam flowing in the fin tubes of the heat exchangergradually condenses to the effect of the cooling air flowing on theexternal, finned side of the heat exchanger. As the condensation andheat extraction is realised directly without a transmitting medium, thisis called direct dry cooling. Naturally safe and controllable directcooling by air that can be technically implemented is a much morecomplex process than this. The process in dry cooling takes place in adecidedly wider temperature range as compared to common water coolingfollowing the significant temperature fluctuations taking place duringthe year in ambient air temperature. This means that on the steam sidesignificantly varying condenser pressure, in other words turbine backpressure will be created. Taking into consideration these varyingtemperature and pressure conditions from the point of view of economy itis necessary to select and operate the equipment optimally, as well asto ensure its operational reliability.

The best known and tried direct cooling by air realises the aboverequirements by breaking down the condensing process into two easilyseparable phases. In accordance with this the steam-air heat exchangerconsists of two parts, the so-called condenser part and the secondarycondenser, which is called an aftercooler or dephlegmator in thespecialist literature.

The steam exits the steam distribution pipes, then goes through thedistribution chambers of the condenser part to the finned heat exchangertubes. The coolant air flows on the external, finned side at rightangles to the longitudinal axis of the pipes, in other wordsperpendicular to the flow direction of the steam. The condenser mayconsist of multi-tubes in the direction of the air, but also of asingle, extended tube. Due to the cooling effect of the air the steamgradually condenses in the tubes. The condensate goes in the samedirection as the steam in a downwards direction due to gravity partiallyflowing on the internal wall of the tube, partially with the flowingsteam to the condensate collection and steam transmission chamberpositioned at the bottom end of the pipes. From here the condensate goesfrom the individual heat exchanger bundles to the condensate pipe. Theremaining uncondensed steam (30-15 percent of the initial amount) andthe unwanted, non-condensing gases present in the steam pass into afurther heat exchanger section, the so-called aftercooler ordephlegmator part.

Significant differences in the degree of condensation and, with this,the concentration of non-condensing gases develop in certain pipesections both with respect to time and space. Changes over time may becaused by a change in the temperature of the external air, a change inthe steam-side loading and the airflow rate. Changes with respect tospace are determined by the positioning of the heat exchanger tubes.Significant differences can develop between individual tubes in theplane perpendicular to the direction of cooling airflow due to theuneven steam or air distribution. Further unevenness is displayed in thedirection of the airflow, as the cooling air gradually warms up and sois able to condense an increasingly smaller amount of steam. This effectdoes not only occur in the case of multiple-tube condensers in the flowdirection, but also in the case of single row condenser tubes that arestretched out in the airflow direction (although to a lesser degree).The non-condensing gases can become concentrated in certain sections ofthe heat exchanger, so-called air-plugs can develop, terminating theflow of steam and so removing the tube section of the given heatexchanger from effective cooling. Besides this performance drop, intemperature conditions under freezing, the freezing up of the heatexchanger and significant operation breakdowns can be caused. Theseproblems of direct cooling by air are known of in the related technicaljournals. (e.g. Kroger, D. G., Air Cooled Heat Exchangers and CoolingTowers, section 8, part 8.2., TECPRESS, 1998).

The problem caused by uneven condensation is reduced by the most widelyused direct air cooled system by inserting a heat exchanger sectioncalled a dephlegmator, which essentially carries out an aftercoolingfunction. As compared to that justified by the design in general asignificantly greater amount of steam is fed from the condenser sectionto the dephlegmator part due to endeavours to overcome the unevenness.The dephlegmator section uses a similar heat exchanger type to that usedin the condensation section, with the significant difference that theinput of the steam does not take place from above but from a lowerdistribution chamber, from which the steam flows upwards in the heatexchanger tubes, in the mean time the condensate flows in the oppositedirection to the effect of gravity to the lower steam distribution andcondensate collection chamber. The circumstances causing unevennesspresented in the case of the condensation section also appear here. Onetypical problem of this section may derive from steam side overloading,which may hold up the condensate flowing downwards due to the effect ofgravity setting up a water plug and so taking out the remaining sectionof the tube from the operation of the heat exchanger. Over and abovethis drop in performance this can cause other operation problems,including freezing up problems in cold weather. In accordance with thisthe dephlegmator section needs to be significantly overdimensioned. Astudy by Goldschagg, H. B. analyses the problems of one of the mostmodern direct air cooled systems in existence (Lessons learned from theworld's largest force draft direct cooling condenser, paper presented atthe EPRI Int. Symp. on Improved Technology for Fossil Power Plants,Washington, March 1993.).

The unwanted, non-condensing gases present in the steam, consistingmainly of air have to be pumped out of the space under vacuum. Thepumping work is reduced if the suction takes place in a place where theratio of the gases in the steam-gas mixture is the greatest. The steamarriving in the upper chamber of the dephlegmator at this point containsten-fifty percent non-condensing gas, so this steam-gas mixture issuitable for the known pumping out using ejectors. Due to the low steamflow rate in the dephlegmator section a relatively low heat transfercoefficient can be attained. This is made significantly worse by theconvective heat transfer which receives an increasing role instead ofcondensation due to the increasing partial pressure of thenon-condensing gases. Besides the heat transfer coefficient a furtherdrop in performance is caused by the reducing steam saturation vapourpressure and temperature due to the increasing partial pressure of thenon-condensable gases, and, due to this, the increasingly smallerlogarithmic temperature difference. The increasing “undercooling” may bea further source of possible freezing up. This risk is discussed by theanalysis in the January 1994 issue of the publication POWER (Swanekamp,R: Profit from latest experience with air-cooled condensers).

A further phenomenon occurring in direct cooling by air duringcondensation is the drop in pressure of the steam (or steam-gas mixture)flowing in the heat exchanger tubes of the condenser and dephlegmator,which also, naturally, depends on the length of the flow route. Thisloss of pressure due to friction also reduces the logarithmictemperature difference, which acts as the driving force from the pointof view of heat transfer, between the cooling medium (air) and thecooled medium (steam). At the same time due to the large specific volumein the case of a direct air condenser of a given size and reducingexternal air temperature a status may come about when due to theincreasing flow losses the reduction of the temperature of the coolingair does not result in the further improvement of cooling performance(so-called choking). The tube length of the heat exchanger sections ofcondensers and dephlegmators in the case of average or greater powerplant cooling is 10 meters for both, in other words the total tubelength is doubled by the dephlegmator section.

The lack of uniformity in both the condenser and the dephlegmator,operation reliability problems and controlling difficulties essentiallyderive from the fact of the so-called direct condensation itself. Thecondensation occurring inside the tubes, in the whole of the coolingsystem, in an extended space sets the amount of steam andsteam—non-condensing gas mixture and vice versa, the obstacles reducing,or even blocking the flow reduce or stop the condensation. The lack offorced circulation on the condensing medium side makes the control ofthe process difficult, and interventions can only take place on theouter side of the heat exchanger, on the cooling air side. This explainswhy direct air cooled condensers have only been constructed with fanstill now. Here the forced circulation of the cooling air gives at leastthe possibility of regulating the airflow. In the case of naturaldraught direct condensers on both medium sides the flow is “natural”, inother words the flow is caused by the process itself, and so the processis nearly uncontrollable—this explains why natural draught direct aircooled systems have never been constructed.

Other direct air cooled systems also exist in which the dephlegmatorsection is not positioned in a separate heat exchanger bundle, but oneof the tubes falling in the flow direction of the air is set up as adephlegmator, or in a so-called “quasi-single tube” system a part in theone tube separated by a wall serves as a dephlegmator. In these casesthe imbalance between the individual tubes increases further, and itbecomes even more difficult to control the whole process than thosepresented earlier using separate condenser-dephlegmator heat exchangerbundles. All this does not change that despite the known and operabledirect air cooling technical solutions there is a need for acondensation part and following that a so-called dephlegmator section(which is actually a similar direct steam-air heat exchanger in whichthe condensation process continues).

It can be determined that the most inefficient, in other words therelatively speaking most expensive part of direct cooling by air is thedephlegmator, which, at the same time, is required for reasons ofacceptable operation reliability and controllability.

A mention still needs to be made of endeavours that increase the aircooling performance of air cooling, mainly the peak performance byspraying the cooling surface of the finned air cooling tubes with water,or by establishing a continuous film of water on them. Such is presentedin the previously referred to Swanekamp publication (POWER, June 1994).

3. THE INVENTION

The aim of the invention is to establish an air cooled system which ascompared to the known direct air cooled solutions improves on the costeffectiveness of these, at the same time as significantly increasingtheir operation reliability, including operation flexibility, and whichmakes it possible to control them even in extreme operation conditions,and furthermore, which increases start-up reliability when operation isstarted.

The air cooled system according to the invention contains a steam-airheat exchanger consisting of tubes finned on the outside suitable forthe partial direct condensing of a medium in the vapour state withambient air, which heat exchanger receives the steam from an upperdistribution chamber and ends in a lower chamber, which collects theamount of condensation according to the condensed steam and the steamthat has not yet condensed, it has at least one direct contact condenserin which the remaining steam that has not yet condensed coming from thelower collection chamber of the steam-air heat exchanger condenses ohthe effect of cooling water cooled in a water-air heat exchanger andsprayed through jets; at the same time the non-condensing gases areremoved from the aforementioned direct contact condenser through asuitably structured tray-type or packed after-cooler.

The cooling of the finned heat exchanger tubes takes place with coolingair made to flow by fans or cooling towers providing a natural draught.The heat exchanger bundles belonging to the cooling air made to flow bya common fan is usually called a cell and a series of cells a “bay”.

Here also as in the known direct air cooled systems the fin tubes areconnected to a lower steam and condensate collection chamber at the endof the tube bundle. The condensation of the remaining, not yet condensedsteam in the steam-air segment of the air cooled system takes place inone or more direct contact condensers with cooling water cooled in awater-air heat exchanger; the direct contact condenser or direct contactcondensers are connected in series with the water-air heat exchanger orheat exchangers and are connected directly to one another. Thecondensate passes into the condensate collection pipe due to the effectof gravity.

The steam flowing into the direct contact condenser condenses on thecooling water sprayed in through the condenser jets and cooled in awater-air heat exchanger and passes into the storage part (hot well) ofthe direct contact condenser together with the heated up cooling water.The pumping out of the non-condensing gases also takes place from thedirect contact condenser space.

So the cooling system according to the invention realises the set aim byremoving the least efficient dephlegmator part used in the knownsolutions and detailed earlier and replacing it with a more efficient,more easily controllable and more reliable solution, the water-aircooling segment of the air cooled system according to the invention. Sothe condensation of the remaining steam is realised in a spacesignificantly smaller than that of the dephlegmator, in a compact directcontact condenser, which as compared to the dephlegmator also providesnear ideal conditions for the removal of the non-condensing gases. Theheat removal at ambient temperature level takes place in theaforementioned forced circulation water-air heat exchanger, into whichonly an insignificant amount of non-condensing gas passes as compared tothe water current. Due to this in the heat exchanger partly because ofthe forced circulation and partly because of the lack of non-condensinggases a heat exchange can be realised that is significantly moreefficient than that in a dephlegmator, more controllable and lesssensitive to operating conditions. At the same time the cooling systemaccording to the invention also retains the more efficient condensationsection. This, naturally, does not mean the mechanical replacement ofthe dephlegmator part used until now, but requires the optimised ratioof the condensation part and the solution replacing the dephlegmatoraccording to the given application. Depending on the applicationcircumstances the condensation section may be reduced to even 30-40percent of its original dimensions, but at the same time it may alsoexceed the proportion in the “condenser-dephlegmator” solution.

The solution that in the air cooled system according to the inventionthe steam that has not condensed in condenser section passes directlyinto the compact steam space of the direct contact condenser makes itpossible to leave out the further steam distribution system used in theknown art. Similarly there is no need for the steam, or steam containingan increasing amount of non-condensing gases as a consequence of thecondensation, to pass through further long, narrow heat exchanger tubes.All this significantly reduces the steam side pressure drop and thetemperature drop involved with this. In the place of the mixture ofsteam and non-condensing gases, there is water in the water-air heatexchanger as the medium to be cooled. This according to the forcedcirculation makes completely uniform medium distribution possible on theinside of the heat exchanger tubes. Also the increasing undercoolingoccurring as a consequence of the partial pressure of air increasing inearlier solutions can be avoided. The heat transfer coefficient on theinternal side of the tube will also be significantly more favourablethan in the case of the condensation of steam with a high non-condensinggas content. All this all in all results in a more efficient heatexchanger with a smaller surface, which also means that it is cheaper.Also as a result of the reduction of undercooling the efficiency of thepower plant cycle is improved to a degree. As the removal of thenon-condensing gases takes place in much more favourable circumstances,in a single space, from the direct contact condenser, the amount thathas to be pumped out is much less, which makes it possible to usesmaller ejectors and less auxiliary energy. The removal of thedephlegmator section also helps ensure a better vacuum by avoidingcooling system “choking” during lower external air temperatures, inother words attaining greater turbine performance. A very significantfurther result due to leaving out the surface heat exchanger sectioncondensing the steam and non-condensing gas mixture is the avoidance ofvarious problematic operation statuses (gas blockages of varying size oreven the formation of water plugs as a consequence of “hold-ups”). Thismakes it possible to avoid numerous operation problems and haveoperation that is more reliable and controllable.

In larger air cooled systems the expanded steam arriving from theturbine passes into several parallel-connected steam-air heatexchangers, that is condensers. In such cases not only one directcontact condenser may be used to condense the remaining steam, butseveral direct contact condensers may be directly connected one to eachof the heat exchanger bundles of the steam-air condenser, and thenconnected on the water side to shorten the steam path.

The steam-air and water-air heat exchanger bundles consisting of finnedheat exchanger tubes may not only be placed in cells separated from oneanother, but also combined in the same cell (so they have a common fan).It is practical here if the individual steam-air heat exchanger bundlesare also directly connected to individual, separate direct contactcondenser spaces.

Of the two serially connected sections of the air cooled system on thesteam side, the replacement of the “rear” dephlegmator section with themore controllable solution presented here assists the controllability ofthe whole process. So in the solution according to the invention in theplace of fans providing the cooling air flow towers inducing a naturaldraught may be used without endangering operation reliability (which wasnot possible in the case of purely direct air cooling condensers, as wepresent in connected with the state of the current art).

In a further version of the invention not only does the non-condensed,remaining steam pass into the direct contact condenser, but the steamcan also pass into it directly from a branch with a valve from theexpanded, main steam pipe or a branch of it so by-passing the condenser.This makes control of the system and selection of the most efficientoperation mode according to the operation requirements easier due to theoptimum loading distribution between the steam-air heat exchanger andthe water-air heat exchanger. In the case of lower ambient temperaturesopening the by-pass pipe and through this sending the loading towardsthe direct contact condenser and the water-air heat exchanger pushes the“choking” phenomenon towards even lower turbine back pressures, andthrough this contribute to a further improvement in performance of thepower plant.

The peak period increase of performance of the air cooled systemaccording to the invention can be attained if the surface of the finnedheat exchanger tubes of the water-air heat exchanger exposed to the flowof cooling air are sprayed with water, or a water film is formed on itby continuous supply. At such a time by opening the aforementionedby-pass pipe valve the heat removal can be partly transferred from thesteam-air heat exchanger segment to the wetted water-air heat exchangersegment, which increases the overall performance of the cooling systemand via this that of the power plant.

It is possibly practical to couple the installation of a steam shut-offdevice to the steam side by-pass pipe in the main steam pipe sectionafter the by-pass pipe branch. As it is known that when starting powerplants using direct air cooled systems at temperatures under freezingpoint only following attaining a minimum steam amount (5-10%) may steambe permitted into the direct air cooled condenser in order to avoid thedanger of freezing. Until this limit value the steam has to be blowninto the air. The solution according to the invention makes the start-upprocess possible even at a zero steam amount. Opening the steam by-passpipe valve and closing the main steam pipe valve makes the start-upprocess possible through the “rear” section (direct contact condenserand water-air heat exchanger) of the serially connected cooling system.As by opening the water cycle by-pass valve it is possible to heat upthe cooling water via the direct contact condenser. At this time thewater-air heat exchanger is not filled up with water, so the pump thatcirculates the cooling water circulates the cooling water through thepipe that bypasses the heat exchanger (when the water side by-pass valvefitted in it is open). The filling of the water-air heat exchangerstakes place with water heated up in this way, and they will only be putinto operation following this. The steam-air heat exchanger (condenser)is only put into operation following the opening of the main steam pipevalve, if the steam flow significantly exceeds the safety value.

In a further advantageous construction form of the solution according tothe invention the lower condensate and steam collection chamber of thesteam-air heat exchanger (condenser) in the first section of the aircooled system is transformed in such a way that the remaining steam isnot fed from the chamber into the body of a separate direct contactcondenser. Instead the lower collection chamber serves as a directcontact condenser space itself by feeding the water cooled down in thewater-air heat exchanger to the jets positioned in the lower chamber (inits entire length or just in certain sections). Due to this thecondensation of the remaining steam takes place in the immediateproximity of exiting from the condenser tubes, in the lower collectionchamber. The removal of the non-condensing gases takes place in asuitably formed section of the chamber, preferably containing atray-type aftercooler. In order to restrict the size of a chamber formedin this way carrying out such a combined task (condensate and remainingsteam collection chamber, direct contact condenser space and spacesuitable for the removal of the non-condensing gases) in one or moreplaces containers need to be installed that serve as the storage part(hot well) of the direct contact condenser for the heated up coolingwater and steam condensate. This solution significantly reduces the pathof the remaining steam leading to condensation, via this reducing thepressure and, consequently, temperature drops occurring as a consequenceof steam friction, as well as the imbalances occurring during this. Itis also possible to place the steam-air and water-air heat exchangers incommon bundles.

A further favourable solution can be constructed with the integration ofthe steam-air and water-air heat exchangers. That is not only in oneheat exchanger bundle but in every single heat exchanger tube there is asegment creating the steam-air heat exchange and the water-air heatexchange as well. This requires a heat exchanger tube that is stretchedin form in the direction of the airflow, and a multifunction lowerchamber that carries out several tasks. The lower chamber collects thecondensate and remaining steam arriving from the steam-air heatexchanger segment and serves as a direct contact condenser space for theremaining steam. The same space contains a tray-type or packedaftercooler assisting the removal of the non-condensing gases. A part ofthe space in the lower chamber also serves as the water distributionchamber of the water-air heat exchanger and it is through this that thecooled water is fed to the jet nozzles. Inside the integrated heatexchanger tube starting from the lower collection chamber a part,favourably the part towards the side of entry of the cooling air, isseparated from the rest of the tube with a side wall in a planeperpendicular to the direction of flow of the air so that it is suitablefor forming the water-air heat exchanger pipe section. It is alsopractical if this section ends in an intermediate point in the length ofthe heat exchanger tube, where it is delimited with a closing componentpositioned in a plane perpendicular to the axis of the tube. Thewater-air heat exchanger tube section formed in this way may be brokendown into further channels with one or more internal separating walls.Using only one internal separating wall, which ends before the upperclosing component, a two-pass cross countercurrent water-air heatexchanger can be formed so that from the point of view of the directionof flow of the air the warmed cooling water flows upwards in the innerchannel, then turning round at the end of the separating wall it flowsdownwards in the outer channel where the air enters and then in themeanwhile cools down as a consequence of the cooling effect provided bythe finned heat exchanger surface. The steam coming from the turbinegets to the steam-air heat exchanger tube through the upper steamdistribution chamber via the whole cross-section of the heat exchangertube. The steam partly condenses in the section remaining for thesteam-air heat exchange, during this not only does the steam flowreduce, but because of the appearance of the water-air heat exchangersection from a certain point the cross-section available for the flowalso reduces. The condensate and the remaining steam go to the lowerchamber of the heat exchanger bundle that carries out the combined taskas presented above. The cooling water cooled down in the outer channelsections is sprayed through the jet nozzles positioned in the lowerchamber into the mixing condenser space of the lower chamber. Here itmeets the remaining steam arriving from the channels serving as asteam-air heat exchanger over the whole of its length and condenses thegreater part of it. In the lower chamber or in a space approaching it ispractical to construct a counter-current tray-type or packedafter-cooler condenser part, from which the non-condensing gases can befed to the ejectors under favourable conditions.

In a further sub-version of this solution the externally finned heatexchanger tube elongated in the direction of the airflow is broken upinto several channels with separating walls. The steam coming from theturbine here also enters the whole cross-section of the heat exchanger,in other words it enters the heat exchanger tube via all of thechannels. Some of these steam-condensation channels run all the way fromthe upper distribution chamber to the lower collection chamber and endthere; the rest of the steam channels start from the upper steamdistribution chamber and end at an intermediate point of the length ofthe heat exchanger pipe. Before the end point of these channels there isa passage opening through the separating wall to the neighbouring steamcondensation channel. In another practical solution there are holes oropenings repeatedly in the separating walls between the channels usedfor steam condensation, due to which holes the condensation part becomequasi-single channelled (similarly to that in patent specificationnumber WO 98/33028). Two or more, but an even number of the channels ofthe multi-channel heat exchanger pipe (two of its channels in the caseof a total of four channels) are separated from the steam space startingfrom the lower end up to a certain height (preferably on the cooling airentry side) and serves to form the water-air heat exchanger section.

The solution described here and its variants via its combined andintegrated functions, as well as its structural units contribute to theestablishment of a more cost-effective and more efficient, due to theavoidance of longer lengths of medium travel, process. As we mentionedsteam may enter in the total tube cross-section of all the tubes formingthe heat exchangers. Naturally, the steam-air heat exchanger needs to bevacuum sealed. So the uniform water-air heat exchangers integrated intoone body with the steam-air sections may also be constructed so thatthey are vacuum sealed. This makes it possible to re-circulate thewarmed up cooling water and for the pressure increase required for thedistribution between the heat exchanger tubes to be of such a degreethat is required to overcome only the friction of the cycle, sopermitting certain sections of the water-air heat exchanger to be underatmospheric pressure. In a heat exchanger formed in this way thecondensation takes place in four steps but in a single heat exchangerbody, partly in the steam-air heat exchanger section, to a lesser extentalong the wall separating the steam and water flow of the individualheat exchanger tubes, with the injection of cooled cooling water in thelower collection chamber also serving as the direct contact condenserspace, and finally in the same place in the tray-type after-coolersection leading to where the air is removed.

A further favourable construction form can be realised in a case usingan integrated heat exchanger partially similar to the previous case,when within the individual tubes an odd number, even just one, ofchannels is formed as a water-air heat exchanger. Then from thecollection chamber that also serves as a direct contact condenser thewarmed up cooling water goes to a storage space, from where the pumptransports it to an external distribution cooling water pipe. It ispractical if the distribution cooling water pipe runs between the heatexchanger bundles arranged in an A form, and from this there arebranches to the channel on the entry side, with respect to the directionof the airflow, of every single tube in an intermediate section of thetubes forming the heat exchanger bundle. The cooling water, in thischannel section flowing from its introductions downwards all the way,cools again and is injected into the lower collection chamber that alsoserves as a direct contact condenser space through nozzles suitable toform jets.

In a further construction form of the integrated heat exchanger thedistribution of the heated cooling water again is carried out in thedistribution section formed in the lower collection chamber and fromhere the water to be cooled flows upwards in one channel up to anintermediate section of the whole length of the channel. The cooledcooling water is injected through the holes or nozzles formed in theupper section of the channel into the neighbouring channel, where itcarries out the condensation of the remaining steam flowing from thecondenser channels through the lower collection chamber into this mixingspace. A pipe of significantly smaller cross-section than that of thecross-section of the channel enters every channel section serving as amixing space “neighbouring” the water cooler channel up to its end. Itis through these pipes that the non-condensing gases that become moreconcentrated in the upper part of the mixing space are sucked out andfed to the collection pipes of the ejection system. This solution givesa favourable result when the conditions justify that the steam-aircondensation is to have a dominant role in the heat exchange as comparedto the water-air heat exchange.

4. DESCRIPTION OF THE POSSIBLE WAYS OF REALISATION OF THE INVENTION ONTHE BASIS OF DRAWINGS

Some favourable constructions of the invention are described in detailedas examples, with the help of figures, where

FIG. 1 shows an air cooled system with a steam-air heat exchanger,water-air heat exchanger and a direct contact condenser,

FIG. 2 shows a natural-draught air cooled system,

FIG. 3 shows an air cooled system where beside the remaining steam ofthe steam-air heat exchanger the direct contact condenser can alsodirectly condense a part of the steam expanded in the turbine,

FIG. 4 shows an air cooled system, where the lower collection chamber ofthe steam-air heat exchanger also serves as a direct contact condenser,

FIG. 5 a shows an air cooled system with integrated heat exchanger tubescontaining a steam-air heat exchanger tube section and a two-pass crosscountercurrent water-air heat exchanger pipe section, which ends at anintermediate point of the length of the pipe

FIG. 5 b shows an A-A section of FIG. 5 a,

FIG. 5 c shows a B-B section of FIG. 5 b,

FIG. 6 a shows an air cooled system with integrated heat exchangertubes, which contain a steam-air heat exchanger section divided intochannels by separating walls, and on the channels ending at anintermediate point of the length of the tube there is a passage opening,and they also contain a two-pass cross countercurrent water-air heatexchanger tube section,

FIG. 6 b shows an A-A section of FIG. 6 a

FIG. 6 c shows a B-B section of FIG. 6 b,

FIG. 7 a shows an air cooled system with integrated heat exchangertubes, which contain a steam-air heat exchanger tube section withcontinuously perforated separating walls, and a two-pass crosscountercurrent water-air heat exchanger tube section, which ends at anintermediate point of the length of the tube,

FIG. 7 b shows an A-A section of FIG. 7 a

FIG. 7 c shows a B-B section of FIG. 7 b,

FIG. 8 a shows an air cooled system with integrated heat exchangertubes, which contain a steam-air heat exchanger tube section and asingle-pass cross flow water-air tube section, the water supply of whichis solved from an external water distribution pipe going between theheat exchanger bundles arranged in an A shape,

FIG. 8 b shows a B-B section of FIG. 8 a,

FIG. 9 a shows an air cooled system with integrated heat exchangertubes, which contain a steam-air heat exchanger tube section, asingle-pass cross flow water-air tube section, the water supply of whichis solved through the lower chamber, and a pipe section situated betweenthe two previously mentioned units, serving as a direct contactcondenser space,

FIG. 9 b shows a B-B section of FIG. 9 a.

The air cooled system in FIG. 1 shows a bundle of the applied steam-airheat exchanger and the water-air heat exchanger each, the direct contactcondenser and the way they are connected to each other. The steam to becondensed 1 expanded in the turbine enters the steam-air heat exchangerbundle 3 through the upper steam distribution chamber 24. From the uppersteam distribution chamber 24 the steam current to be condensed 21enters each finned tube of the aforementioned steam-air heat exchangerbundle, which finned tubes serve as air-cooled condensers 2. Flowingthrough the finned steam-air heat exchanger tube 2 a part of the steamis condensed as a result of the cooling effect of the ambient coolingair 4 moved by the fan 5 (or by some other air moving unit). Thecondensate 8 and the remaining steam current 22 enter the lowercollection chamber 25 from the steam-air heat exchanger tube 2. Theaccumulated remaining steam 23 does not enter a further steam-air heatexchanger to be condensed there, but it enters a rather compact directcontact condenser 9 connected to the lower collection chamber 25. Thecooling water jets entered into the direct contact condenser through thenozzles 10 serve as a surface realising the condensation of theaccumulated remaining steam 23. The mixture of the cooling water, whichwarmed up in the course of the condensation, and the steam condensed inthe direct contact condenser 9 are accumulated in the storage part 15(hot well). The tray-type or packed aftercooler 37, which helps theremoval of the non-condensed gases is situated in an appropriate part ofthe direct contact condenser 9. The non-condensed gases are pumped outfrom the aftercooler 37 by ejector pumps, through the air removal pipe11. From the storage part 15 of the direct contact condenser the water,the amount of which is in proportion with the condensed steam, and thecondensate 8 from the lower collection chamber 25 of the steam-air heatexchanger 3 enter a condensate pipe. From the storage part 15 of thedirect contact condenser 9 the warmed up cooling water 13 is carried tothe water-air heat exchanger bundle 7 by a cooling water extraction andcirculating pump 14. The warmed up cooling water current 13 is cooledagain by the cooling air 4 moved by the fan 5 in the finned tubes 6 ofthe water-air heat exchanger 7. Practically the recooling takes place ina two-pass cross countercurrent heat exchanger. The cooling watercurrent 12 recooled in the water-air heat exchanger 7 is injected intothe direct contact condenser 9 space through the aforementioned nozzles10. Due to the cyclic process ending like this the dephlegmator used inthe known solutions becomes unnecessary.

In the case of tasks demanding greater heat removal the air cooledsystem shown in FIG. 1 is modified so that the expanded steam 1 arrivingfrom the turbine 20 is distributed into several steam-air heatexchangers 3, that is condensers, parallel connected to each other. Insuch cases not only one direct contact condenser 9 can be used, but adirect contact condenser 9 can be indirectly connected to each of theheat exchanger bundles of the steam-air condenser 3 separately, so thatthey can be connected on the water side in order to shorten the steampaths.

In FIG. 1 the steam-air 3 and water-air 7 heat exchanger bundles areshown separated from each other, and in accordance with this they havetheir own fan 5 each. At the same time it is also possible to place thesteam-air 3 and water-air 7 heat exchanger bundles combined with eachother in one single cell, and in this case they have a common fan 5.

FIG. 2 shows a solution similar to the one shown in FIG. 1, with thedifference that the fans 5 used for moving the cooling air 4 in FIG. 1are replaced by a cooling tower structure inducing natural draught 5 a.Instead of the forced circulation of the air it is made possible to usenatural draught so that on the medium side there is the forcedcirculation water-air heat exchanger bundle 7 and the direct contactcondenser 9 during the most critical stage; and the condensation of theremaining steam 23 and the removal of the non-condensed gases is solvedin or from the direct contact condenser space 9, which can be regardedas compact. As a result of this the influence of external circumstances(air temperature, wind velocity, etc.) is reduced, and the processremains controllable.

The construction example in FIG. 3 shows a construction where the steamto be condensed 1 can get through the steam-air heat exchanger bundle 3in the form of remaining steam 23, and also through a by-pass steam pipe26 and through a steam valve 27 situated in it, directly into the directcontact condenser space 9. It significantly improves the controllabilityof the whole of the cooling system and the selection of the optimaloperating mode. If a shut-off valve 28 is also fitted in the main steamdistributing pipe, by shutting it off favourable conditions can beensured even in the case that the temperature is below zero when thepower plant block is started, and the cooling system can be startedsafely and water can be saved. In such cases the start-up takes place atthe rear part of the serially connected cooling system, that is throughthe direct contact condenser 9 and the water-air heat exchanger 7. Whenthe power plant block is started, the water-air heat exchangers are notfilled, and the cooling water current flows through only one by-passpipe, until it is heated to the appropriate temperature. Only after thisare the water-air heat exchangers 7 filled and put into operation. Thesteam-air heat exchanger 3 is put into operation by opening the shut-offvalve 28, when the steam current 1 has significantly exceeded the safevalue needed for frost-free operation.

FIG. 4 shows a further favourable construction example, where the lowercondensate and remaining steam collecting chamber 29 of the steam-airheat exchanger bundle 3 also provides the condensing space of the directcontact condenser. In this way, as opposed to the earlier constructionexamples shown in FIGS. 1, 2 and 3, no separate direct contact condenserunit 9 is needed. Instead the cooled water current 12 is injectedthrough a line of nozzles 10 situated in the lower collection chamber29. In this way the condensation of the remaining steam currents 22discharged from the steam-air heat exchanger tubes 2 and the removal ofthe non-condensed gases 11 do not simply take place in a separate,otherwise compact direct contact condenser, but without any movement, inthe combined lower collection chamber 29 and direct contact condenserspace—reducing the losses caused by movements even more. In order torestrict the size of the chamber 29 the container serving as thehot-well of the direct contact condenser 15 must be created to admit thewarmed up cooling water 13 and the steam condensate 8 a.

FIGS. 5 a, b, c, 6 a, b, c és 7 a, b, c show an even higher level of theintegration of the functions and the realisation of the process. Themost important characteristic feature of these solutions is thecombination of the steam-air 3 and the water-air 7 heat exchangers sothat they are not only integrated inside one heat exchanger bundle, butinside each finned heat exchanger tube of the heat exchanger bundles.Consequently each integrated finned heat exchanger tube 39 of theintegrated air-cooled heat exchanger bundle has a tube section realisingsteam-air heat exchange 35 a and a pipe section realising water-air heatexchange 35 b.

A further important element increasing integration and the combinationof the steam-air and water-air cooling unit is a combined-function lowerchamber 30, in which the remaining steam 22 arriving from the steam-airsection 35 a and the condensate 8 a are collected; it also serves as adirect contact condenser space as a result of the fact that the cooledcooling water is injected through the nozzles 10 situated here; theaftercooler 37 helping the removal of the non-condensed gases is alsosituated here (or in a space closely connected to it), as well as thecooling water distribution space 36 of the water-air heat exchanger tubesection 35 b. Practically the aftercooler 37 is a tray-type or packeddevice suitable for countercurrent heat and mass transfer. Both sectionsof the integrated heat exchanger tube 39 have a heat exchanger surfaceof the same type of geometry, and in accordance with this, similarly tothe steam-air heat exchanger pipe section 35 a, the water-air heatexchanger section 35 b can also be made in a vacuum tight way. In thisway the pump 14 a used for circulating the warmed up cooling water canbe a simple circulation pump instead of the so-called extraction andcirculation pump.

Inside the integrated heat exchanger tube 39 the water-air heatexchanger tube section 35 b is created so that starting from thecombined lower chamber 30 a part—practically the part on the side wherethe cooling air 4 enters—is delimited with a side wall 32 from the otherpart of the tube, in a plane perpendicular to the flow direction of theair 4. Furthermore, practically this water-air section 35 b ends at anintermediate point of the length of the integrated heat exchanger tube39, which is delimited at the top by a closing component situated in aplace perpendicular to axis of the integrated heat exchanger tube 39. Asa result of this from the upper steam distribution chamber 24 the steamcurrent 21 can enter the steam-air heat exchanger tube section using thecomplete cross-section of the integrated heat exchanger tube 39.

Inside the finned heat exchanger tubes the separate but integratedconstruction of the steam-air heat exchanger section 39 and thewater-air heat exchanger section 35 b can be favourable promoted byapplying the finned heat exchanger tubes elongated in the flow directionof the cooling air, and by creating channels with separating wallsinside the provided cross-section 39, where the channels divide the heatexchanger tube into parts, and in the channels, in accordance with theirfunction stated in the construction examples, the steam medium of thesteam-air cooling section and the cooling water medium of the water-aircooling section are conducted.

In the construction examples shown in FIGS. 5 a, b, c and in the figuresdescribed below the heat exchanger pipes according to the invention aredivided into channels described above.

The water-air heat exchanger tube section 35 b constructed as above canbe divided into further channels with separating walls. If there is oneinternal separating wall 34 (which separating wall 34 ends before itreaches the closing component 33), then a two-pass cross countercurrentwater-air heat exchanger can be constructed so that with respect to theflow direction of the air 4 the warmed up cooling water 13 flows upwardsin the inner channel, then turning back in the space between the end ofthe separating wall 34 and the closing component 33 it flows downwardsin the outer channel on the side where the air enters. During this, as aresult of the cooling effect of the surface of the finned integratedheat exchanger tube 39 the cooling water is cools down.

By placing another separating wall 34 the water-air heat exchangersegment 35 b can be divided into even more paths of an even number.

In accordance with the above the construction example of the coolingsystem shown in FIGS. 5 a, b, c and its integrated heat exchanger tube39 contains a steam-air heat exchanger section 35 a and the water-airheat exchanger section 35 b delimited by a closing component 33 and aside wall 32. The water-air heat exchanger section 35 b is divided intotwo paths by a separating wall 34. The water being cooled flows upwardsin the inner channel with respect to the flow direction of the coolingair, and it flows downwards in the outer channel. (In FIG. 5 c the watermedium is marked with lines, the flow of direction is upwards ascompared to the plane of the drawing, marked with sign “−”, anddownwards as compared to the plane of the drawing, marked with sign“+”.) The remaining space part 35 a of the integrated heat exchangertube 39 creates the steam-air heat exchanger tube section, in which thesteam to be condensed flows downwards. (In FIG. 5 c the steam medium isin the channel not marked with lines, the flow of direction is downwardsas compared to the plane of the drawing, marked with sign “+”).According to the above description from the upper steam distributionchamber 24 the steam 21 enters the steam-air heat exchanger tube section35 a through the whole cross-section of the integrated heat exchangertube 39. Flowing through the whole cross-section the steam 21 graduallycondenses, and at the top point of the water-air heat exchanger section35 b (which is the closing component 33) cross-section of the steam-airheat exchanger section 35 a obviously decreases, but here the volumeflow rate of the steam is significantly lower. The remaining steamleaving the steam-air cooling section 35 a is condensed further by thecooled water taken from the water-air section 35 b and injected into thesteam through a nozzle 10, and cooling water-condensed water mixturecoming from the steam-air cooling section and created as a result of theinjection arrives at the combined collection chamber serving also as adirect contact condenser 30 and enters the storage space 15.Non-condensed gases are removed from the vacuum tight chamber 30 throughthe aftercooler 37. An amount in proportion with the cooling water iscarried from the cooling water-condensate mixture collected in thechamber 30 and in its storage space 15 by a circulation pump into thedistribution space 36, from where it is taken back to the water-air heatexchanger section 35 b.

In the case of a version of the solution described in connection withFIGS. 5 a, b, c shown in FIGS. 6 a, b, c the steam-air heat exchangertube section 35 a is divided into parallel channels with furtherseparating walls 31 placed in the planes perpendicular to the flowdirection of the cooling air. Certain channels of the steam-air heatexchanger tube section 35 a do not run along the whole length of thechannel, but they end at the upper closing component 33 of the water-airheat exchanger tube section 35 b. At the end of the separating walls 31of these channels there are openings 41. The steam or condensate flowingin these channels can enter the neighbouring channels through theseopenings.

In FIGS. 7 a, b, c a version of the construction example described inconnection with FIGS. 5 abc is shown, where the internal space of theintegrated heat exchanger tube 39 containing the a steam-air and awater-air section is divided into parallel channels with separatingwalls 31 a in the flow direction of the cooling air, situated in a planeperpendicular to the flow direction, where the walls 31 a separatingcertain channels of the steam-air heat exchanger tube segment 35 a arecontinuously pierced and perforated in order to make the condensationspace a single-channel space.

FIGS. 8 a,b show a favourable construction example where similarly toFIGS. 5 abc, 6 abc and 7 abc the heat exchanger bundle 40 and each ofits heat exchanger tubes 39 a are elements realising integrated steamcondensation and water cooling. At the same time the admission of thewarmed up cooling water 13 is passed into the water-air heat exchangertube section 35 b placed in the outer channel of the heat exchangertubes 39 a from a cooling water distribution pipe 42 led between theheat exchanger bundles 40 arranged in an A shape, in parallel with theplane of the bundles and with the centre-line of the upper steamdistribution chamber 24. The cooling water flows downwards and isrecooled in the water-air heat exchanger tube section 35 b, and it isinjected through nozzles 10 into the combined lower collection chamberand direct contact condenser space 29 a. In accordance with this, withrespect to the ratio between the steam-air and water-air heat exchangingthis solution is practically suitable in the case of a greaterproportion. It must be pointed out that the water-air heat exchangerpipe segment 35 b can be divided into further paths with two or moreseparating plates of an even number, in a way that in the last path thecooling water flows downwards as described above, and at the end of thechannel it is injected into the combined lower collection chamber 29 athrough nozzles 10.

FIGS. 9 a,b show a further construction example where similarly to FIGS.5 a, b, c, 6 a, b, c, 7 a, b, c and 8 a,b an integrated steam-air andwater-air heat exchanger bundle 40 is applied, which consists ofintegrated-function heat exchanger tubes 39 b. Similarly to FIGS. 8 a,b,inside the heat exchanger tube 39 b the water-air heat exchanger section35 b uses only one water cooling channel 35 b. This channel is also theouter channel of the heat exchanger pipe 39 b situated on the side wherethe cooling air is entered. Furthermore the water-air heat exchangersection 35 b does not run along the whole length of the heat exchangertube in this case either, but at an intermediate height it is delimitedwith an upper closing component 33 from the steam-air heat exchangersection 35 a. However, the warmed up cooling water 13 is not admittedthrough a distribution pipe outside the heat exchanger bundle, but withthe help of a water distribution space part 36 a made in the lowercollection chamber 25 a. Unlike in the case of the solution described inFIG. 8, in this case the cooling water flows upwards, and the recoolingprocess ends as the water reaches the upper part of the water-air heatexchanger section 35 b. From here the cooling water is injected throughnozzles 10 into a heat exchanger pipe section forming a neighbouringcombined steam-air condenser and direct contact condenser space 35 c. Atthe top the section serving as a combined steam condenser and mixingcondenser space 35 c is also delimited with an upper closing component33, while on the one side it is separated from the water-air heatexchanger tube section 35 b with a separating wall 32, and on the otherside it is separated from the steam-air heat exchanger pipe section 35 awith another separating wall 43. The remaining steam enters the lowercollection chamber 25 a from the channels of the steam-air heatexchanger tube section 35 a (condenser part) running along its wholelength, then it changes direction and it flows upwards in the sectionserving as a combined steam condenser and direct contact condenser space35 c, until it condenses as a result of the cooling water injectedthrough nozzles from the water-air heat exchanger section 35 b. Thenon-condensed gases become concentrated in the upper part of the heatexchanger tube section forming the condensing space 35 c. These gasesare removed by air removing pipes 44 of a small diameter, running alongthe section forming the condensing space 35 c. These air removing pipesjoin the air removing collecting pipe 45 placed in the combined-functionlower chamber 25 a, and from there they get to the ejector systemthrough air removal 11.

5. SUMMARY

The air cooled system according to the invention, which contains asteam-air cooling section consisting of finned heat exchanger tubes anda serially connected water-air cooling section consisting of finned heatexchanger tubes shows significant advantages as compared to directcooling by air containing common steam-air heat exchangers only, as aresult of

-   -   adapting to external circumstances,    -   the possibility to omit dephlegmators,    -   increasing the flexibility and safety of operation,    -   increasing controllability,    -   the possibility to decrease establishment costs.

In the air cooled system according to the invention the integration ofthe steam-air cooling section and the water-air cooling section in theirfinned heat exchanger tubes results in a further significant increase ofthe above advantages.

1. A combined air cooled condenser for processing a vaporized mediumfrom a vapor source, the condenser comprising: a first cooling volumeconnected to the vapor source for receiving the vaporized medium fromthe vapor source and constituting means for performing partialcondensation of the vaporized medium resulting in a first condensate, aresidual vapor, and non-condensables, the first cooling volume beingcooled by a gaseous cooling medium; a direct contact condenser connectedin series to the first cooling volume, the direct contact condensercomprising at least one condenser stage for condensing the residualvapor from the first cooling volume by spraying cooling water therebyconverting the residual vapor from the first cooling volume into asecond condensate and concentrated non-condensables with vapor; and asecond cooling volume connected to the direct contact condenser forreceiving the cooling water from the direct contact condenser and forobtaining a cooled down cooling water to be supplied to the directcontact condenser, the second cooling volume being cooled by the gaseouscooling medium; the direct contact condenser being connected in serieswith the first and second cooling volumes and further comprising a firstoutlet for recirculating a first stream of the first and secondcondensates for reuse, a second outlet for providing a second stream ofthe cooling water to be supplied to the second cooling volume and athird outlet including an ejector for ejecting the concentratednon-condensables; wherein the first cooling volume and the directcontact condenser are connected in series with each other and the vaporsource and the connection between the first cooling volume and thedirect contact condenser is dimensioned such that vaporized medium fromthe vapor source first passes through the first cooling volume as afirst condenser stage and then after partial condensation to the directcontact condenser as a second condenser stage.
 2. A combined air cooledcondenser according to claim 1, wherein the first cooling volume isdefined by a steam-air heat exchanger comprising a series of heatexchanger tubes connected between an upper distribution chamber fordistributing the steam among the heat exchanger tubes and a lowercollection chamber for collecting the first condensate, the remainingsteam and the non-condensables obtained from the heat exchanger tubes.3. A combined air cooled condenser according to claim 1, wherein thesecond cooling volume is defined by a water-air heat exchangercomprising a water inlet, a water outlet and a series of heat exchangertubes connected to the water inlet and the water outlet.
 4. A combinedair cooled condenser according to claim 1, wherein the direct contactcondenser further comprises: a main condensing section with sprayingnozzles for spraying cooling water onto the remaining steam; acounter-flow tray-type or packed after-cooler part for condensing in asecond stage the remaining steam and concentrating the non-condensablesto a level required by the ejector; and a storage part for collecting atleast a part of the first condensate, the second condensate and thesprayed cooling water.
 5. A combined air cooled condenser according toclaim 4, wherein the first cooling volume defined by a steam-air heatexchanger and the direct contact condenser are separate units connectedto each other directly in series and wherein the lower collectionchamber is provided with an outlet for recirculating a stream of thefirst condensate for reuse, and the direct contact condenser has anoutlet for recirculating a stream of the second condensate for reuse. 6.A combined air cooled condenser according to claim 4, wherein the lowercollecting chamber and the direct contact condenser are combined witheach other, wherein the lower collecting chamber has an enlarged volumefor both collecting the first condensate, the remaining steam and thenon-condensables obtained from the heat exchanger tubes and foraccommodating the spraying nozzles for spraying cooling water onto themixture of residual steam and non-condensables, the lower collectingchamber being directly connected to the storage part of the directcontact condenser wherein the storage part has an outlet for providingthe first stream of the first and second condensates for reuse, and forproviding the second stream of the cooling water to be supplied to thesecond cooling volume and a venting outlet for removing the concentratednon-condensables.
 7. A combined air cooled condenser according to claim5, wherein at least a part of the vaporized medium is lead to the directcontact condenser directly through a first by-pass pipe by opening avalve in the first by-pass pipe and the cooling water collected in thestorage part of the direct contact condenser can be returned directly tothe direct contact condenser through a second by-pass pipe by opening asecond valve in the second by-pass pipe.
 8. A combined air cooledcondenser according to claim 7, wherein the amount of the vaporizedmedium is regulated by a shut-off valve arranged in the main steamdistributing pipe.
 9. A combined air cooled condenser according to claim1, wherein the first cooling volume defined by a steam-air heatexchanger and the second cooling volume defined by a water-air heatexchanger are integrated in one integrated heat exchanger unit,comprising integrated heat exchanger tubes with an elongatedcross-section divided by a first separating wall into a first tubesegment for performing steam-air heat exchange and a second tube segmentfor performing water-air heat exchange.
 10. A combined air cooledcondenser according to claim 9, wherein the tube segment performingwater-air heat exchange extends at the lower end into the combinedcollecting chamber and direct contact condenser; and at the upper end,which is closed by a closing component, into the integrated heatexchanger tube up to an intermediate point, thereby reducing thecross-section of the combined heat exchanger tube in a lower region,wherein a part of the tube section performing water-air heat exchange isdivided into two channels by a second separating wall extending from alower portion of the first separating wall and having a length forleaving an opening at the closing component.
 11. A combined air cooledcondenser according to claim 10, wherein the water-air heat exchangersegment is arranged on the air cooled side of the combined heatexchanger tube so that the cooling water entering the water-air heatexchanger segment flows upwards in the inner channel and flows downwardsin the outer channel and the first separating wall is connected to thespraying nozzles of the direct contact condenser in a region below thesecond separation wall.
 12. A combined air cooled condenser according toclaim 9, wherein the combined lower collecting chamber with a directcontact condenser function has an enlarged volume for both collectingthe first condensate obtained from the combined heat exchanger tubes andfor accommodating the spraying nozzles for spraying cooling water ontothe residual steam, the lower collecting chamber being directlyconnected to the storage part of the direct contact condenser whereinthe storage part has an outlet for providing a first stream of the firstand second condensates for reuse, and for providing second stream ofcooling water to be supplied to the second cooling volume and a ventingoutlet for removing the concentrated non-condensables.
 13. A combinedair cooled condenser according to claim 9, wherein the inner space ofthe integrated heat exchanger tube is divided into parallel channels bythird separating walls extending from the upper end of the integratedheat exchanger tube and having a length for leaving an opening at theclosing component through which the steam and the condensate can flowfreely into the channels running along the whole length of the heatexchanger tube.
 14. A combined air cooled condenser according to claim13, wherein at least a part of the third separating walls areperforated.
 15. A combined air cooled condenser according to claim 9,wherein the tube segment performing water-air heat exchange extends atthe lower end into the combined collecting chamber and direct contactcondenser; and at the upper end, which is closed by a closing component,into the integrated heat exchanger tube up to an intermediate point,thereby reducing the cross-section of the combined heat exchanger tubein a lower region, wherein the tube segment performing water-air heatexchange is a single channel segment which is connected on the aircooled side in an upper region to an external warmed up cooling waterdistribution pipe, which in turn is connected to the storage part of thedirect contact condenser and the first separating wall being providedwith spraying nozzles in a lower region.
 16. A combined air cooledcondenser according to claim 9, wherein the integrated heat exchangertube has three segments separated by separating walls into a steam-airheat exchanger tube segment; a water-air heat exchanger tube segment,where the cooling water flowing upwards from the water distributionchamber part of the combined collection chamber is sprayed throughnozzles situated at the end of the water-air heat exchanger tubesegment, into the third neighboring heat exchanger tube segment servingas a direct contact condenser space; from the upper end of the thirdtube segment a removal pipe is placed running along the whole length ofthe third segment, led through and out of the combined lower chamber toremove the concentrated non-condensables.
 17. A combined air cooledcondenser according to claim 1, wherein the gaseous cooling medium isdriven towards the first and second cooling volumes by fans.
 18. Acombined air cooled condenser according to claim 1, wherein the gaseouscooling medium is driven towards the first and second cooling volumes bya natural draft tower.
 19. A combined air cooled condenser according toclaim 3, wherein a surface of the water-air heat exchanger is made wetwith water sprayed into the cooling air, or a continuous water film isformed on the surface of the water-air heat exchanger.
 20. A combinedair cooled condenser according to claim 1, wherein the gaseous coolingmedium is air.
 21. A combined air cooled condenser according to claim 6,wherein at least a part of the vaporized medium is lead to the directcontact condenser directly through a first by-pass pipe by opening avalve in the first by-pass pipe and the cooling water collected in thestorage part of the direct contact condenser can be returned directly tothe direct contact condenser through a second by-pass pipe by opening asecond valve in the second by-pass pipe.
 22. A combined air cooledcondenser as claimed in claim 1 wherein said vapor source is a steamturbine.